System and method for performing an in-service software upgrade in non-redundant systems

ABSTRACT

An information handling system is provided. The information handling system includes one or more devices coupled together to route information between the one or more devices and other devices coupled thereto based on routing information stored in the one or more devices. The one or more devices includes a routing processor, one or more line cards coupled to the routing processor, the one or more line cards receiving the routing information from the routing processor for routing data packets to a destination, and a memory coupled to the routing processor. The routing processor is configured to create an active image having a current state of the routing information and create a standby image having the current state of the routing information, wherein the standby image requests the current state of the routing information from the active image using a key that is calculated using a portion of the routing information.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/460,436, filed Apr. 30, 2012, which is hereby incorporated byreference in its entirety.

BACKGROUND

1. Technical Field

The present disclosure is related to systems and methods for performingin-service software upgrades. In particular, embodiments disclosedherein are related to systems and methods for performing in-servicesoftware upgrades in non-redundant systems and/or in informationhandling systems.

2. Discussion of Related Art

As the value and use of information continues to increase, individualsand businesses seek additional ways to process and store information.One option available to users is information handling systems. Aninformation handling system generally processes, compiles, stores,and/or communicates information or data for business, personal, or otherpurposes thereby allowing users to take advantage of the value of theinformation. Because technology and information handling needs andrequirements vary between different users or applications, informationhandling systems may also vary regarding what information is handled,how the information is handled, how much information is processed,stored, or communicated, and how quickly and efficiently the informationmay be processed, stored, or communicated. The variations in informationhandling systems allow for information handling systems to be general orconfigured for a specific user or specific use such as financialtransaction processing, airline reservations, enterprise data storage,or global communications. In addition, information handling systems mayinclude a variety of hardware and software components that may beconfigured to process, store, and communicate information and mayinclude one or more computer systems, data storage systems, andnetworking systems.

However, certain information handling systems, include devices that donot have redundant hardware for preventing traffic loss in case of adevice failure or for when the device goes offline to receive a softwareupgrade. Such systems are unable to achieve a stateful switchover andthe result is significant traffic loss while the device is offline orreceiving a software upgrade. What is needed is a system and method forperforming in-service software upgrades in a non-redundant system thatachieves a stateful switch over and minimizes traffic loss.

SUMMARY

Consistent with some embodiments, there is provided an informationhandling system. The information handling system includes one or moredevices coupled together to route information between the one or moredevices and other devices coupled thereto based on routing informationstored in the one or more devices. At least one of the one or moredevices includes a routing processor, one or more line cards coupled tothe routing processor, the one or more line cards receiving the routinginformation from the routing processor for routing data packets to adestination, and a memory coupled to the routing processor. The routingprocessor is configured to create an active image having a current stateof the routing information and create a standby image having the currentstate of the routing information, wherein the standby image requests thecurrent state of the routing information from the active image using akey that is calculated using a portion of the routing information.

Consistent with some embodiments, there is also provided a method ofperforming an in-service software upgrade in a non-redundant systemhaving a processor and a memory. The method includes creating an activeimage and a standby image, the active image and the standby image eachincluding a table stored in the memory, generating, an index for datareceived by the active image, and transmitting the received data to thestandby image. The method also includes calculating a key based on thedata, saving, by the active image, a first tuple including the data, theindex, and the key in the active image table, transmitting, by theactive image, the index and data corresponding to a key received fromthe standby image, and saving, by the standby image, a second tupleincluding the index and the data received from the active image, and thekey sent to the active image, in the standby active image table. Themethod further includes switching control from the active image and thestandby image when the active image receives a software upgrade.

Consistent with some embodiments, there is further provided a devicehaving a processor and a memory, the memory including instructions thatwhen executed by the processor cause the processor to perform a method.The method includes creating an active image and a standby image, theactive image having control of the device, creating an active imagetable and a standby image table, the active image table and the standbyimage table storing information related to the operation of device, andtransmitting a data value received by the active image to the standbyimage. The method also includes generating, by the active image, anindex for the received data value, calculating, by the active image andthe standby image, a key based on the received data value, storing, bythe active image, the received data value, the generated index, and thecalculated key in the standby image table, transmitting, by the activeimage, the received data value and the generated index to the standbyimage in response to a request received from the standby image includingthe calculated key, and storing, by the standby image, the received datavalue, the generated index, and the calculated key in the standby imagetable. The method further includes switching control of the device fromthe active image to the standby image when the active image becomesinactive.

These and other embodiments will be described in further detail belowwith respect to the following figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an information handling system consistent with someembodiments.

FIG. 2, is a diagram illustrating a device having redundant routingprocessors for providing minimal packet loss during an in-servicesoftware upgrade, consistent with some embodiments

FIG. 3 is a diagram illustrating an in-service software upgradeperformed on a device, consistent with some embodiments.

FIG. 4 is a diagram illustrating performing an in-service softwareupgrade on a non-redundant system, consistent with some embodiments.

FIG. 5 is a diagram illustrating performing an in-service softwareupgrade on a non-redundant system, consistent with some embodiments.

FIG. 6 is a flowchart illustrating a method for performing an in-servicesoftware upgrade, consistent with some embodiments.

In the drawings, elements having the same designation have the same orsimilar functions.

DETAILED DESCRIPTION

In the following description specific details are set forth describingcertain embodiments. It will be apparent, however, to one skilled in theart that the disclosed embodiments may be practiced without some or allof these specific details. The specific embodiments presented are meantto be illustrative, but not limiting. One skilled in the art may realizeother material that, although not specifically described herein, iswithin the scope and spirit of this disclosure.

For purposes of this disclosure, an information handling system mayinclude any instrumentality or aggregate of instrumentalities operableto compute, classify, process, transmit, receive, retrieve, originate,switch, store, display, manifest, detect, record, reproduce, handle, orutilize any form of information, intelligence, or data for business,scientific, control, or other purposes. For example, an informationhandling system may be a personal computer, a network storage device, orany other suitable device and may vary in size, shape, performance,functionality, and price. The information handling system may includerandom access memory (RAM), one or more processing resources such as acentral processing unit (CPU) or hardware or software control logic,ROM, and/or other types of nonvolatile memory. Additional components ofthe information handling system may include one or more disk drives, oneor more network ports for communicating with external devices as well asvarious input and output (I/O) devices, such as a keyboard, a mouse, anda video display. The information handling system may also include one ormore buses operable to transmit communications between the varioushardware components.

FIG. 1 shows an information handling system consistent with someembodiments. As shown in FIG. 1, information handling system 100includes a plurality of devices 102-1-102-N coupled to each other in alinked or aggregated arrangement. Consistent with some embodiments,devices 102-1-102-N may include any appropriate combination of hardwareand/or software having a processor and capable of reading instructionsstored on a non-transitory machine-readable medium for execution by theprocessor. Consistent with some embodiments devices 102-1-102-N includea machine-readable medium, such as a memory (not shown) that includesinstructions for execution by a processor (not shown) for causingdevices 102-1-102-N to perform specific tasks. For example, suchinstructions may include handling and routing information. Inparticular, devices 102-1-102-N may be configured to route and forwarddata packets based on [index, value] tuples describing a destination ofthe data packets. Some common forms of machine-readable media includes,for example, floppy disk, flexible disk, hard disk, magnetic tape, anyother magnetic medium, CD-ROM, any other optical medium, punch cards,paper tape, any other physical medium with patterns of holes, RAM, PROM,EPROM, FLASH-EPROM, any other memory chip or cartridge, and/or any othermedium from which a processor or computer is adapted to read.

Consistent with some embodiments, devices 102-1 to 102-N are coupledtogether to transmit information between each other and to other devicescoupled to devices 102-1-102-N. System 100 may represent a local areanetwork, a wide area network, or a link aggregation group. When any ofdevice 102-1-102-N require a software upgrade, it is desirable tominimize or eliminate any downtime on the routing device in order toprevent the loss of any data. In particular, the goal of an In-ServiceSoftware Upgrade (ISSU) is to enable upgrading or downgrading therunning software image on a platform configured with redundantsupervisors providing minimal packet loss. In some network systems, ISSUmay be achieved by incorporating redundant switching/routing engines orrouting processors (RPs) in the system. FIG. 2, is a diagramillustrating device 102-N having redundant routing processors forproviding minimal packet loss during an ISSU, consistent with someembodiments.

As shown in FIG. 2, device 102-N includes a first routing processor 202and a second routing processor 204 both coupled to a source 206 and aline card 208. Line card 208 may represent one or more line cards.Routing processors 202 and 204 may also be coupled to each other, andmay be configured to provide routing information for line card 208 todirect packets received from a source 206 to a destination 210. Inparticular, routing processors 202 and 204 may be configured tocalculate hardware and software tables that reflect states in theforwarding/routing tables as an (index, value) tuple.

FIG. 3 is a diagram illustrating an in-service software upgradeperformed on device 102-N, consistent with some embodiments. As shown inFIG. 3, routing processor 202 may be configured to be an “active”processor, while routing processor 204 may be configured to be a“standby” processor. Active routing processor 202 maintains a softwaretable 302 and a hardware table 304 representing, for example, thecurrent state of the hardware of device 102-N (e.g., TCAM or othermemories) required for a software upgrade modeled most simply as aseries of (index, value) tuples that are stored in software table 302and hardware table 304 and represent addresses for forwarding androuting packets. Each time the state of the hardware changes, activerouting processor 202 accepts a request for a new value, and calculatesan index for the new value. This new index and value tuple issynchronized with standby routing processor 204 and stored in softwaretable 306 and hardware table 308 of standby routing processor 204. Thissynchronization ensures that standby routing processor 204 always hasstored the latest view of the state of the hardware. Accordingly, whenrouting device 102-N receives a software upgrade or otherwise fails oris taken offline, standby routing processor 204 becomes the activeprocessor while active routing processor 204 goes offline and undergoesthe upgrade. Because standby routing processor 204 was beingsynchronized with active routing processor 202 and had stored the latestview of the state of the hardware, standby routing processor 204 canseamlessly take over the functions of active routing processor 202without the loss of data. Consequently, standby routing processor 204 isconsidered to be “standby hot” and device 102-N is capable of statefulswitchover (SSO). Once the software upgrade of active routing processor202 is completed, it will become the standby processor that issynchronized with processor 204. Once the synchronization is complete,processor 202 can return to being the active routing processor whileprocessor 204 receives the software upgrade.

The system shown in FIG. 3 utilizes two separate processors, activeprocessor 202 and standby processor 204, each having related memory forstoring software tables 302 and 306 and hardware tables 304 and 308.However, using two separate processors as a redundancy increases thecosts associated with routing devices 102-N and system 100. In-servicesoftware upgrades may be achieved by using Virtual Machines (VMs) forthe active processor and standby processor 204. However, VMs are notsupported on all processor architectures and may require additionalmemory or a faster CPU.

FIG. 4 is a diagram illustrating performing an in-service softwareupgrade on a non-redundant system, consistent with some embodiments.In-service software upgrades for non-redundant systems poses interestingchallenges since there is only one set of hardware resources. That is,there is typically only a single processor and memory in a device 400undergoing a software upgrade. In order to perform an in-servicesoftware upgrade, conventional non-redundant systems may create a copyof the hardware tables 402 just before the upgrade, undergo the upgrade,and then rewrite the copied hardware tables 402. In particular,conventional systems may create a “standby” image 404 that learns thestate of the hardware from the existing image, which is referred to asthe “active” image 406. After standby image 404 has learned the state ofthe hardware, active image 406 exits and standby image 404 assumescontrol of the hardware, essentially becoming the new active image. Forthe purposes of an in-service upgrade, the hardware, typically ternarycontent addressable memory (TCAM) or other memories, required for theupgrade process can be viewed as hardware table 404, and is modeled mostsimply as a series of (index, value) tuples. When a request is made fora new value in the hardware, an index is computed for that value, andthe (index, value) tuple is stored in software table 408 of active image406. Bringing standby image 404 into coherence with active image 406typically involves making one request for each value currently stored inhardware table 402 and in software table 408, and then saving therequested (index, value) tuple in software table 410. Once all requestshave been issued, standby image 404 will have a model of hardware table402 in software table 410 that performs the same function as thecurrently programmed hardware in hardware table 402. Then, when activeimage 406 receives an upgrade, control may pass to standby image 404,which is now the active image that has a model of hardware table 402stored in software table 410, while the active image 406 receives theupgrade.

However, the computation of the index depends on the value being stored,other values that have been stored, and values that have been stored butwhich have been deleted. In other words, the index of a value does notdepend solely on the values being programmed into hardware table 402,but on the historical values that were once programmed. This means thatstandby image 404 may not have an entirely accurate view of the physicalprogramming of the hardware stored in software table 410, which meansthat standby image 404 cannot assume control of the hardware under thesecircumstances. In particular, a problem is how to supply a softwareframework that allows standby image 404 to acquire an accurate view ofthe hardware without re-writing hardware tables 402 from scratch usingsoftware table 410. Moreover, since standby image 404 does not havedirect access to and cannot control hardware table 402, a predeterminedamount of memory equal to the size of hardware table is set aside forsoftware table 410 and is emulated as hardware. However, in the event ofa failover, all traffic is halted, all of the values in hardware table402 are re-written with the values stored in software table 410 so thatsoftware table 410 and hardware table 402 are consistent, and trafficcan be restarted. The problem with this approach is that it takesadditional memory resources and it may take several seconds to re-writeall the hardware tables resulting in a tangible traffic loss. As aresult standby image 402 is not considered to be “standby hot” anddevice 400 cannot achieve a stateful switchover (SSO) from active image402 to standby image 404.

FIG. 5 is a diagram illustrating performing an in-service softwareupgrade on a non-redundant system using (index, value, key) tuples,consistent with some embodiments. As shown in FIG. 5, a device 500undergoing an in-service software upgrade models the existing hardwareof device 500 as an (index, value, key) tuple, where the index and valueare the same as in FIGS. 3 and 4, and the key is an object that isderived from the request and which uniquely identifies the tuple.Consistent with some embodiments, active image 502 creates a tuple everytime it programs a new entry into the hardware table 504, and saves acopy of the created tuple in software table 506 along with a calculatedkey. Moreover, active image 502 may be configured to retrieve a tuplesaved in software table 506 based on its key.

As shown in FIG. 5, a standby image 508 having a software table 510 isalso created, similar to FIG. 4. Consistent with some embodiments,active image 502 may be configured to transmit a copy of the entryprogrammed into hardware table 504 to standby image 508. When standbyimage 508 receives this entry, standby image 508 may be configured tocompute the key associated with that entry, and requests thecorresponding tuple stored in software table 506 from active image 506.As a result, software table 510 of standby image 508 will always be thesame as software table 506 of active image, and both will always be thesame as hardware table 504, ensuring that both standby image 508 andactive image 502 always have the same view of the hardware of device500. Then, when active image 502 receives an upgrade, control may passto standby image 508, which is now an active image that has a correctand up to date model of hardware table 504 stored in software table 510,while active image 502 receives the upgrade. Consequently, when anin-service software upgrade is performed on active image 502, standbyimage 504 has a correct view of the hardware, and there will be nointerruption of the hardware behavior resulting in a “near hitless”takeover of the hardware and a stateful switchover (SSO).

FIG. 6 is a flowchart illustrating a method for performing an in-servicesoftware upgrade, consistent with some embodiments. For the purpose ofillustration, FIG. 6 will be discussed in conjunction with FIG. 5. Asshown in FIG. 6, the method for performing an in-service softwareupgrade includes steps that are performed by active image 502 and bystandby image 508. Moreover, consistent with some embodiments, the rolesof “active” image and “standby” image may switch between what iscurrently referred to as active image 502 and standby image 508 whenactive image 502 exits and undergoes an upgrade and standby image 508assumes control and becomes the new “active” image. As shown in FIG. 6,the method begins when active image 502 adds a new data entry intohardware table 504 (602). Consistent with some embodiments, the new dataentry may represent a new state of the hardware of device 500. The newdata entry is then transmitted to standby image 508 in order tosynchronize standby image 508 with active image 502 (604). Standby image508 receives the new data entry from active image 502 (606) andcalculates a key based on the received data entry (608). Consistent withsome embodiments, the key may be calculated by using a predeterminedfunction of the received data entry.

Meanwhile, active image 502 generates an index for the new data entry(610). Consistent with some embodiments, the generated index isgenerated as an opaque data type. An opaque data type is a data typethat is incompletely defined in an interface, so that its values canonly be manipulated by calling subroutines that have access to themissing information. In other words, an opaque data type does not have adata type associated with it such that it appears as basically atypeless data object. By generating the index as an opaque data type,existing and future systems can be changed to operate similar to thesystem shown in FIG. 5 and the method described in FIG. 6 such thatexisting software codes, designed without the requirement for in-serviceupgrades, can be easily transformed to support near hitless in-serviceupgrades. In particular, methods that handle an index (such as shown inFIGS. 3 and 4) can be changed at the hardware programming interface tohandle an opaque index instead of the index. Moreover, a compiler mayidentify all instances of an index to be changed such that instead ofhandling an index and computing an address, an opaque type index isreturned instead. Consistent with some embodiments, the key may berequired to generate the index. As a side-effect of generating the indexusing the key, the key may be verified as unique and the (index, key)tuple may be stored for later retrieval.

Returning to FIG. 6, active image 502 then calculates a key based on thenew data entry (612). Consistent with some embodiments, the key may becalculated by using a predetermined function of the new data entry.According to some embodiments, the predetermined function may be thesame function that is used by standby image 508 to calculate a key instep 608. After calculating the key and generating the index for the newdata entry, active image now has a complete (index, value, key) tuple,and saves this tuple to software table 506 (614). In order to maintainan up to date and active view of hardware table 504, standby image 508requests the generated index and data entry value from active image 502using the calculated key (616). Active image 502 receives the key fromstandby image 508 as a request for the generated index and data entryvalue (618). Using the key received from standby image 508, active image502 performs a lookup operation in software table 506 for thecorresponding index and value to the key received from standby image 508(620). The index and value corresponding to the received key is thentransmitted to standby image 508 (622). Standby image receives the indexand value corresponding to the calculated key (624) and, now having acomplete (index, value, key) tuple, saves the tuple to software table510 (626). The steps will repeat each time a new data entry is added inhardware table 504 so that software table 510 of standby image 508 willalways have an exact copy of software table 506 of active image 502 and,thus an up to date and accurate view of the current state of thehardware. Since standby image 508 always has an exact copy of softwaretable 506 of active image 502, when active image 502 receives anupgrade, control can seamlessly switch over to standby image such thatthe transition is near hitless. Consistent with some embodiments, anin-service software upgrade may be performed during a maintenance windowand may take between 5 through 30 minutes to complete, as long as thetraffic disruption is minimal.

The system shown in FIG. 5 and the method described in FIG. 6 may allowa system to perform a near hit-less software upgrade. Further, sincestandby image 508 always know the states of the hardware, standby imageis considered to be “standby hot” such that standby image 508 can takeover for active image 502 if active image 502 goes down. As a result thesystem shown in FIG. 5 using the method described in FIG. 6 may be usedto achieve stateful switchover (SSO) process level redundancy.

Unlike the system shown in FIG. 4, the system shown in FIG. 5implementing the method shown in FIG. 6 does not require any additionalsystem resources and, since software table 510 is always synchronizedwith hardware table 504, there is no need to re-write the values inhardware table 504 when a failover occurs, resulting in minimal trafficloss. Further, the system shown in FIG. 5 implementing the method shownin FIG. 6 does not require or utilize virtual machines and, thus, can bemade processor architecture independent. Indeed, the system shown inFIG. 5 and the method shown in FIG. 6 may be used in any device havinghardware and software capable of executing the steps shown in FIG. 6 andthat would benefit from such a method when performing an in-servicesoftware upgrade. For example, in symmetric multiprocessor (SMP) systemswith multicore CPUs where the system is configured for process affinitysuch that an active process is running on one core and a standby processis running on another core, the method shown in FIG. 6 may be utilizedsuch that the active core and the standby core correspond to activeimage 502 and standby image 508.

One particular application in which the system of FIG. 5 and methoddescribed in FIG. 6 may be used is as an on-going redundancy mechanismin a distributed forwarding switching system where packets are forwardedbased on an index and value, such as system 100 shown in FIG. 1. Inparticular, the system of FIG. 5 and method described in FIG. 6 may beused in a device 102-N such that active image 502 and standby image 508replace the need for two routing processors 202 and 204 shown in FIG. 2.Instead, a single routing processor may be used to create both activeimage 502 and standby image 508, providing significant savings in thecosts, size, and power consumption of a device such as device 102-N.

Consistent with embodiments described herein, there is provided systemsand methods that perform an in-service software upgrade on non-redundantsystems such that the upgrade is near hitless and stateful switchovermay be achieved. The systems and methods described herein may beimplemented on existing and future systems using opaque data types andmay provide a system that achieves stateful switchover without usingadditional hardware or hardware resources. The examples provided aboveare exemplary only and are not intended to be limiting. One skilled inthe art may readily devise other systems consistent with the disclosedembodiments which are intended to be within the scope of thisdisclosure. As such, the application is limited only by the followingclaims.

What is claimed is:
 1. A network device having a processor and a memory,the memory including instructions that when executed by the processorcause the processor to perform a method comprising: maintaining anactive image and a standby image, the active image having control of thedevice; receiving, by the active image, a data value representing anentry in a routing or forwarding table, the entry comprising an addressused for routing and forwarding data packets: providing, by the activeimage, the data value to the standby image; determining, by the activeimage, an index for the data value, the index being based on a positionof the data value within a first routing or forwarding table maintainedby the active image; calculating, by the active image, a first key as afunction of only the data value; storing, by the active image, the datavalue, the index, and the first key in the first routing or forwardingtable; calculating, by the standby image, a second key as a function ofonly the data value; receiving, by the active image, a request for theindex and the data value from the standby image, the request includingthe second key; providing, by the active image in response to receivingthe request from the standby image, the data value and the index to thestandby image when the first key matches the second key; storing, by thestandby image, the data value, the index, and the second key in thesecond routing or forwarding table; and switching control of the devicefrom the active image to the standby image when the active image becomesinactive.
 2. The device of claim 1, wherein the active image becomesinactive based on one or more selected from a croup consisting of afailure of the active image and when a software upgrade is received. 3.The device of claim 1, wherein the index for the data value comprises anopaque data type index.
 4. The device of claim 1, wherein switchingcontrol of the device from the active image to the standby image is nearhitless and stateful.
 5. The device of claim
 1. wherein the index isgenerated using the first key.
 6. The device of claim 1, wherein thedata value, the index, and the first key are stored as a tuple.
 7. Amethod of performing an in-service software upgrade in a network devicehaving a processor and a memory, comprising: maintaining, by theprocessor, an active image and a standby image, the active image havingcontrol of the network device; receiving, by the active image, a datavalue representing an entry in a routing or forwarding table, the entrycomprising an address used for routing and forwarding data packets:providing, by the active image, the data value to the standby image;determining, by the active image, an index for the data value, the indexbeing based on a position of the data value within a first routing orforwarding table maintained by the active image; calculating, by theactive image, a first key as a function of only the data value; storing,by the active image, the data value, the index, and the first key in thefirst routing or forwarding table; calculating, by the standby image, asecond key as a function of only the data value; receiving, by theactive image, a request for the index and the data value from thestandby image, the request including the second key; providing, by theactive image in response to receiving the request from the standbyimage, the data value and the index to the standby image when the firstkey matches the second key; storing, by the standby image, the datavalue, the index, and the second key in the second routing or forwardingtable; and switching control of the network device from the active imageto the standby image when the active image becomes inactive.
 8. Themethod of claim 7, wherein the active image becomes inactive based onone or more selected from a group consisting of a failure of the activeimage and when a software upgrade is received.
 9. The method of claim 7,wherein determining the index for the data value comprises generating anopaque data type index.
 10. The method of claim 7, wherein switchingcontrol of the network device from the active image to the standby imageis near hitless and stateful.
 11. The method of claim 7, wherein theindex is generated using the first key.
 12. The method of claim 7,wherein storing the data value, the index, and the first key by theactive image comprises storing the data value, the index, and the firstkey as a tuple.
 13. An information handling system, comprising: one ormore network devices coupled together to route information between theone or more network devices and other network devices coupled theretobased on routing information stored in the one or more network devices,wherein a first device of the one or more network devices comprises: arouting processor; one or more line cards coupled to the routingprocessor, the one or more line cards receiving the routing informationfrom the routing processor for routing data packets to a destination;and a memory coupled to the routing processor, wherein the routingprocessor is configured to: maintain an active image and a standbyimage, the active image having control of the first device; receive, bythe active image, a data value representing an entry in a routing orforwarding table, the entry comprising an address used for routing andforwarding data packets: provide, by the active image, the data value tothe standby image; determine, by the active image, an index for the datavalue, the index being based on a position of the data value within afirst routing or forwarding table maintained by the active image;calculate, by the active image, a first key as a function of only thedata value; store, by the active image, the data value, the index, andthe first key in the first routing or forwarding table; calculate, bythe standby image, a second key as a function of only the data value;receive, by the active image, a request for the index and the data valuefrom the standby image, the request including the second key; provide,by the active image in response to receiving the request from thestandby image, the data value and the index to the standby image whenthe first key matches the second key; store, by the standby image, thedata value, the index, and the second key in the second routing orforwarding table; and switch control of the first device from the activeimage to the standby image when the active image becomes inactive. 14.The information handling system of claim 13, wherein the active imagebecomes inactive based on one or more selected from a group consistingof a failure of the active image and when a software upgrade isreceived.
 15. The information handling system of claim 13, wherein theswitch of control from the active image to the standby image isstateful.
 16. The information handling system of claim 13, wherein therouting processor is further configured to generate the index using thefirst key.
 17. The information handling system of claim 13, wherein therouting processor is further configured to store the data value, theindex, and the first key as a tuple.